Tool handle switch



United States Patent 3,312,801 TOOL HANDLE SWITCH Harold E. Schleicher, West Hartford, Conn., assignor to the Arrow-Hart & Hegernan Electric Company, Hartford, Conn., a corporation of Connecticut Filed Mar. 10, 1965, Ser. No. 438,583 Claims. (Cl. 20068) This invention relates to electric switches and, more particularly, to electric switches operable by pressure on a finger piece or trigger available outside of the handle or casing of the electric device controlled by the switch while the switch is contained inside the housing or handle. The invention also relates to such switches which are capable of ampere 125 volt ratings.

This invention is an improvement on the switch disclosed in the patent application of David W. Johnson filed Mar. 31, 1964, Ser. No. 356,099 copending herewith and owned by the assignee hereof, now abandoned in favor of a continuation-in-part application Ser. No. 509,256 filed Oct. 25, 1965, in which generic claims are presented covering the invention of this application and the structure in that application.

Switches for use in tool handles prior to said Johnson invention either had lower ratings than the present invention, or were too large for use in tool handles of usual size, or could be held in dead-center position. Sometimes prior switches suffered all of these disadvantages.

Therefore, one object common to this invention and to said Johnson invention is to produce a compact doublepole double-throw switch with butt-type contacts capable of a rating of 20 amperes at 125 volts AC. and capable of use also in many applications of direct current work.

Another object is to provide a switch having the above characteristics which will not hang on a dead-center position.

Another object is to produce a switch having the above characteristics which can be made small enough to fit conveniently into the handle of a portable tool of usual size.

Under some conditions of use of the prior switch, arcing would occur at the fulcrum point where the movable contact pivoted on the fulcrum causing a carbon build-up and increasing the resistance to a point whereat sometimes-the circuit would not be completed.

Thus, an object of this invention is to provide an improved electrical connection between the movable contact and the fulcrum point to avoid arcing and maintain a constant low resistance connection between the movable contact and its fulcrum.

Another object is to provide improved switching action and less contact bounce, thus to reduce arcing and wear and to prolong the lift of the switch contacts.

Other objects and advantages of the invention will appear as it is described in connection with the accompanying drawing.

In the drawing:

FIG. 1 is a side elevation view of a switch embodying the invention, partly broken away and partly in section along line I-I of FIG. 2.

FIG. 2 is atop plan view of the invention as embodied in FIG. 1 with the cover and actuating mechanism removed.

FIG. 3 is a detail perspective view of the spring used to move the movable switch contact from one position to another. a

. FIG. 4 is a perspective view of a movable contact and fulcrum mounting therefor embodying the invention.

FIG. 5 is a perspective view of the fulcrum-saddle and brush-contact member.

Referring to the drawing, the switch contacts and their associated parts are housed in an insulating base or cas- Q 3,312,801 Ce Patented Apr. 4, 1967 ing 10 made of molded insulating material and hollowed out for the reception of the fixed and movable contacts, their associated parts and wire terminals. The casing is symmetrically formed with a central spine or dividing wall 12 on each side of which is a recess, such as 12a and 12b, running the length of the casing but of irregular depth along it. The dividing wall 12 is solid except for its midportion which comprises a pair of parallel thin walls 14 and 16 between which is a narrow longitudinal recess 15 to receive and guide the movement of a contact carrier or operating cradle, as hereinafter fully described.

In the longitudinal recesses 12a and 12b at each end of the casing is a pair of combined fixed contact-andterminal members 20, 20 and 30, 30'.

The members 20, 20 are Z-shape, each having a terminal screw 21 or 21 in its upper outwardly extending portion and a butt-contact button 22 or 22' on the upper surface of its lower inwardly extending portion at the floor level of the casing.

The members 30, 30' are of substantially L-shape, each having an upstanding leg 31, 31' slidable into place in the casing with its edges fitting into oppositely facing slots 23 in the side walls of the end portion of the left end (as viewed in FIG. 2) of the longitudinal recesses 12a and 12b.

The other leg of each member 30, 30' extends inwardlyand lies on the floor of the casing and has a butt-contact button 32 or 32' mounted on its upper surface.

The movable contact member 40, 40' is tiltably mounted in the midportion of each of the longitudinal recesses 12a and 1211. On the lower surface at each end of each movable contact member is mounted a butt-contact button such as 41 and 42 for engagement with the fixed contacts 32, 22, respectively, and in alternation so that when buttons 42, 22 are engaged, 41, 32 are disengaged.

To support the movable contact members tiltably at their midpoints, combined terminal and fulcrum members such as 50 are provided, preferably stamped from sheet metal in form as shown in FIG. 4. A terminal portion 52 extends beneath the floor of the casing in channels or recesses such as 16 formed in the bottom outside surface of the casing beneath the fixed contact members 20,20 and extending into a point midway between the buttons (e.g. buttons 22' and 23).

At the opposite end of the member 50 from the ful crurn, terminal screws, such as 52s, are mounted.

The fulcrum members are held in place in the bottom recesses by a stamped sheet insulation plate 54 which extends across the casing in a recess in the bottom surface of the casing and lies flush against the midportion of both of the combined'fulcrum and terminal members. The plate 54 is held by a screwbolt 55 or rivet, or other securing means that passes through a bore in the casing and through a casting or frame member which is held over the upper surface of the casing.

The inner end 56 of the fulcrum-terminal members 50 is bent up at a right angle and is bifurcated to form a fulcrum support for the movable contact member 40.

Y The movable contact 40 is rigid and is stamped from sheet metal in concave form as shown in FIG. 4 with a central ridge or saddle 46, the underside of which seats on the fulcrum 56 from which the contact extends in opposite directions, with the contact buttons 41, 42 being mounted on theunderside of the extending ends.

In order to improve the contact making and breaking action and minimize the tendency of the movable contact buttons to bounce as they engage the fixed contacts, a resilient strip 48 of thin sheet metal or leaf spring is assembled upon the upper surface of the movable contact 40 across the concavity of the rigid contact 40. The cen- 'strips 48 on the movable contact members from one side to the other of the fulcrum points.

The semi-spherical ends of the sliders 57 provide substantially point contacts with the surface of the flexible strip 48 to minimize friction and minimize the possibility of the holding of the movable contact on dead-center. The insulating sliders 57 are resiliently pressed against the strips 48 by coiled compression springs (not shown).

The ope-rating cradle is molded from insulating material with a top plate 61 positioned across the top of the casing parallel to the casing floor. Depending from the under surface near opposite edges of the plate 61 are projections 62 which contain circular wells in which the aforesaid compression springs (not shown) seat. The diameter of the wells is sufiicient to permit the sliders to telescope into the projections when the switch is assembled and to be guided by the walls of the projection as the slider moves toward and from the operating cradle during the movement of the sliders over the surface of the movable contacts.

In order to move the operating cradle and sliders with a quick make and break action over the fulcrum line, a U-shaped spring 65 is mounted on the operating cradle. The U-spring is stamped from flat spring metal into the shape best illustrated in FIG. 3 with T-shaped heads 66, 66'. The spring is mounted on the operating cradle by insertion through an I-shaped aperture running lengthwise of the casing in the center of the top plate of the cradle. The central portion of the 1 passes entirely through the plate portion 61 of the operating cradle, but the lateral portions of the I pass only partway through the plate portion 61, thus forming shoulders 67 on which the lateral extensions of the heads 66, 66' of the spring come to rest.

Due to the central part of the aperture passing entirely through the plate portion 61 of the operating cradle, the T-heads 66, 66' of the U-spring are permitted limited movement within the aperture.

Finger pressure is transmitted to one or the other of the T-heads ofthe spring by a small finger 71 which projects downwardly from the end of an actuating link 70 into the space between the T-heads of the spring. The link 70 extends longitudinally along and over the top of an insulating liner plate 72 that lies on top of the casing and covers the open portion of the top surface of the casing. The link 70 is connected at one end by a pin 73 to a pivoted finger piece or trigger 74 of conventional form which is, in turn, pivotally mounted on a molded insulation frame member 80 by a pin 76.

The. frame 80 is formed with a hollow portion overlying the top insulation plate 72 and providing a passageway between that plate and the frame in which the link 70 can move longitudinally as the trigger 74 is pressed and released. To return the trigger, link, cradle and movable switch contacts to initial position, a coiled compression return spring 77 of conventional form is provided between the trigger and the frame.

For securing the frame upon the casing, there is provided, in addition to the securing bolt or means 55, another securing bolt or conventional securing means 79 which passes through apertures and passages in the frame 80, the liner plate 72 and base 10.

In moving the switch from the position of FIG. 1, as the trigger is depressed, the actuating finger 71 is pressed against the head 66 of the spring 65. This imposes stress on the other arm of the U-spring and causes its head 66' to press against the operating cradle without the equalizing pressure of the other head 66, thus tending to move it to the left. When this stress is sufiicient to overcome the friction of the sliders 57 against the strips 48 of the movable contacts 40, 40 and to cause the sliders to ride over the fulcrum, the movable contacts will tilt from the position of FIG. 1 to the position wherein the contact buttons 41, 41 engage fixed contact buttons 32, 32'.

On release of the trigger, the return spring 77 will return the trigger to the position of FIG. 1 and reverse action of the operating cradle 60 will cause the movable contacts to return to the FIG. 1 position.

Although the terminal-fulcrum member 50 and the movable contact 40' are both conductive current-carrying parts, the connection between them at the fulcrum point is not adequate for all uses of the invention. In some instances, arcing occurs and there is a carbon build up as .the lubricant becomes carbonized at the fulcrum point.

Under certain conditions, this increases the resistance sufficiently to prevent completion of the circuit or passage of enough current to operate devices controlled by the switch. To avoid this condition, brush or rubbing contact-type fingers 59', 59 are provided which press against opposite longitudinal edges of the movable contact assembly, assisting in centering the movable contact assembly and constantly maintaining self-cleaning rubbing-contact engagement with the movable contact. As shown best in FIG. 5, the fingers are connected together by a transverse portion 51, the whole being preferably a U-shaped thin sheet metal stamping which is riveted, welded or otherwise suitably secured to the terminal-fulcrum member 40 adjacent the fulcrum point.

Extending from one side of the transverse portion 51 and bent up perpendicularly to the plane thereof is an extension which is bent adjacent its extremity, semicylindrically, to form a fulcrum-saddle 53 which rests upon the fulcrum support portion 56 of the fulcrumterminal members 50. The saddle forms a smooth rounded surface for the central ridge 46- of the tiltable contact to rest and pivot upon. This overcomes the tendency of the tiltable contact to pivot on sharp corners of a square or pointed stamping which has caused arcing. This new type of pivot structure and side arm brush contacting guarantees good electrical contacting even under vibration and shock conditions.

Many modifications within the scope of the invention will occur to those skilled in the art. Therefore, the invention is not limited to the specific embodiment i1- lustrated and described.

What is claimed is:

1. In an electric switch, fixed contacts, tiltable contact means engageable with one or another of said fixed contacts alternately, an operating member movable to cause tilting of said tiltable contact means, said tiltable means comprising a concave rig-id member and a resilient member extending across the concavity of said rigid member and secured to the rigid member at its ends, a fulcrumterminal member having a fulcrum portion supporting said contact means tiltably, said operating member engaging said resilient member and being movable from one side of said fulcrum to the other to operate said tiltable contact member and resilient means conductively attached to said terminal means and rubbing against said tiltable contact means in a direction transverse to the tilting so as to maintain a clean conductive connection between said terminal means and'said tiltable contact means, said resilient means also having a portion forming a smooth rounded seat for said tiltable contact means, said seat being supported by the fulcrum portion of said fulcrumterminal member.

2. In an electric switch having a casing, fixed contacts mounted in said casing, tiltable contact means engageable with one or another of said fixed contacts alternately, an operating member movable to cause tilting of said tiltable contact means, a fulcrum-terminal mem'ber having a fulcrum portion supporting said tiltable contact means and having terminal means, acne-piece resilient member conductively attached to said terminal means and having arms pressing oppositely against said tiltable contact means as the latter moves from one position to another to maintain a clean conductive connection from said terminal portion to said contact means, said resilient member also having a portion forming a smooth rounded seat for said tiltable contact means, said seat being supported by the fulcrum portion of said fulcrum-terminal member.

3. In an electric switch, fixed contacts, tiltable contact means engageable with one or another of said fixed contacts alternately, an operating member movable to cause tilting of said tiltable contact means, said tiltable means comprising a concave rigid member having a rounded pivot ridge and a leaf-spring member having an uninterrupted flat central portion extending across said rigid member over said ridge, a contact button at each end of said rigid member securing the ends of said resilient member to said rigid member, a fulcrum-terminal member having a fulcrum portion supporting said contact means tiltably, said operating member engaging said resilient member and being slidable along said flat portion from one side of said fulcrum portion to the other to operate said tiltable contact member, and means to cause uninterrupted sliding of said operating member across said resilient member with a snap action causing quick over-center tilting action of said tiltable contact member, said ieaf spring acting to overcome bouncing of said movable contact when engaging the fixed contact.

4. An electric switch as claimed in claim 3 having means to maintain a continuous current path from said fulcrum-terminal member to said tiltable contact means, comprising resilient conductive fingers on opposite sides of said tiltable contact means adjacent said fulcrum portion and pressing against said tiltable contact means in opposite directions, and means connecting said conductive fingers physically and electrically with said terminal-fulcrum member.

5. An electric switch as claimed in claim 3 having resilient means conductively attached to said terminal means and rubbing against said tiltable contact means in a direction transverse to the tilting so as to maintain a clean conductive connection between said terminal means and said tiltable contact means, said resilient means also having :a portion forming a smooth rounded seat for said tiltable contact means, said seat being supported by the fulcrum portion of said fulcrum-terminal member.

References Cited by the Examiner UNITED STATES PATENTS 922,360 5/ 1909 Trumbull. 2,203,555 6/1940 Von Hoorn 200-68 2,248,361 7/1941 Krieger 200-68 3,117,197 1/1964 Carling et al. ZOO-67 ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, Assistant Examiner. 

1. IN AN ELECTRIC SWITCH, FIXED CONTACTS, TILTABLE CONTACT MEANS ENGAGEABLE WITH ONE OR ANOTHER OF SAID FIXED CONTACTS ALTERNATELY, AN OPERATING MEMBER MOVABLE TO CAUSE TILTING OF SAID TILTABLE CONTACT MEANS, SAID TILTABLE MEANS COMPRISING A CONCAVE RIGID MEMBER AND A RESILIENT MEMBER EXTENDING ACROSS THE CONCAVITY OF SAID RIGID MEMBER AND SECURED TO THE RIGID MEMBER AT ITS ENDS, A FULCRUMTERMINAL MEMBER HAVING A FULCRUM PORTION SUPPORTING SAID CONTACT MEANS TILTABLY, SAID OPERATING MEMBER ENGAGING SAID RESILIENT MEMBER AND BEING MOVABLE FROM ONE SIDE OF SAID FULCRUM TO THE OTHER TO OPERATE SAID TILTABLE CONTACT MEMBER AND RESILIENT MEANS CONDUCTIVELY ATTACHED TO SAID TERMINAL MEANS AND RUBBING AGAINST SAID TILTABLE CONTACT MEANS IN A DIRECTION TRANSVERSE TO THE TILTING SO AS TO MAINTAIN A CLEAN CONDUCTIVE CONNECTION BETWEEN SAID TERMINAL MEANS AND SAID TILTABLE CONTACT MEANS, SAID RESILIENT MEANS ALSO HAVING A PORTION FORMING A SMOOTH ROUNDED SEAT FOR SAID TILTABLE CONTACT MEANS, SAID SEAT BEING SUPPORTED BY THE FULCRUM PORTION OF SAID FULCRUMTERMINAL MEMBER. 